1. Field of the Invention
The present invention relates to a method of acquiring a phalange edge image and a system therefor, and more particularly, to a method of acquiring a phalange edge image extracted from an X-ray image of a hand, and a system therefor.
This work was supported by the IT R&D program of MIC/IITA [2005-S-069-02, Development of Wearable System Using Physiological Signal Processing]
2. Description of the Related Art
A technique for acquiring a phalange edge image extracted from an X-ray image is used to determine the bone age of a child.
As living standards improve, children's adult heights thereof generally increase. Short children, and their parents, worry that they will be short as adults. Therefore, child growth research has developed a technique for predicting the adult height of a child and a medical treatment for increasing adult height.
A child's adult height is predicted based on their bone age. Bone age is not a chronological age but a physiological age. The bone ages of persons who are completely grown are assumed to be equal. Therefore, bone age can be used to determine the remaining potential growth time of a child. If the bone age is larger than the chronological age, the remaining potential growth time is short, and the child has less opportunity to grow.
The bone age prediction method has been especially actively researched in Europe, where the Greulich-Pyle (GP) method based on atlas and the Tanner-Whitehouse (TW) method using a skeletal maturity score are widely used. The TW method is more objective than the GP method, and thus is most widely used. The TW method has been enhanced into the TW2 method, and in 2000, the TW3 method. If a child is predicted to have a short adult height, this can be increased through medical growth treatment. Methods of growth treatment include enhancing bone growth by injecting a growth hormone and prolonging the potential bone growth time.
In the TW3 method, radius, ulna, and short (RUS) bone scores and a carpal score are obtained by adding maturity scores of bone growth plates in the X-ray image of a hand. Generally, maturity stages of bone growth plate are divided into nine stages A to I, and each maturity stage is allocated a maturity score. A doctor determines the maturity stage of a bone using the TW3 method and calculates the maturity score thereof. Maturity scores of bones are added to calculate the RUS scores and the carpal score, giving the bone age of a child.
The results of determining the maturity stage differ among doctors, and even vary over time for the same doctor. Therefore, a more objective method of determining the bone maturity stage using a computer algorithm is required. Some bone maturity stage determination apparatuses using a computer algorithm have already been developed and used in clinics.
Most of the bone maturity stage determination apparatuses used in clinics are provided with only a tool for supporting a doctor to determine a TW3 bone age from an X-ray image, but not an automatic bone maturity determination unit. In addition, even in a bone maturity stage determination apparatus having a bone maturity determination function, a doctor needs to perform some operations. Even in a bone maturity stage determination apparatus having the automatic bone maturity determination unit, the result of the determination depends on the state of the X-ray imaging apparatus and the direction of the hand in the X-ray image, preventing the bone maturity from being determined accurately.
The bone maturity determination is performed by identifying and evaluating the change of shapes of epiphysis and metaphysis of the bone growth plate and a coupling state thereof. Since the shapes of the epiphysis and the metaphysis of the bone growth plate cannot be easily extracted from the X-ray image, it is difficult to implement the automatic bone maturity stage determination apparatus.
In general, in order to extract the shapes of the epiphysis and the metaphysis, a finger edge is detected, and after that, an edge detection mask is applied. Alternatively, a gray level threshold method may be used. When applying the edge detection mask to the epiphysis, the difference in the gray level between the epiphysis and the soft tissue background in the X-ray image is small, and thus the edge cannot be easily detected. On the other hand, when using the gray level threshold method, the threshold cannot be accurately set due to variations in the brightness of the neighboring soft tissue.
Therefore, a technique for accurately extracting the shapes of the epiphysis and the metaphysis from the X-ray image of a hand has been continuously researched. If the soft tissue background is removed from the X-ray image of the hand, the edges of the epiphysis and the metaphysis can be more easily extracted. Theoretically, using a dual-energy x-ray absorptiometry technique, an image of only the bone or soft tissue can be obtained. However, the image of only the bone or soft tissue cannot be accurately obtained by general X-ray absorption imaging techniques.